Cellular communication networks enable user equipment (UE) 101, such as cellular phones and similar computing devices, to communicate using spread spectrum radio frequency communication. As shown in FIG. 1, the UE 101 communicates directly with a radio access network (RAN). The RAN includes a set of base stations such as evolved universal terrestrial radio access network (E-UTRAN) nodes, referred to as E-UTRAN node B or eNodeB 103. FIG. 1 is a diagram of an example architecture for a cellular communication system consistent with 3GPP standardized cellular communication architecture including an example UE 101 communicating with a eNodeB 103 of the network. The eNodeB 103 interfaces with a packet core network or evolved packet core (EPC) 115 that connects the UE to other devices in the cellular communication network and with devices external to the cellular communication network.
The EPC 115 and its components are responsible for enabling communication between the UE 101 and other devices both internal and external to the cellular communication system. The EPC 115 includes a serving gateway (S-GW) 105, a packet gateway (P-GW) 107, a mobility management entity (MME) 109 and similar components. Additional components are part of the EPC 115 (e.g., a home subscriber service (HSS)), but the components with less relevance to the handling of the UE 101 and its mobility have been excluded for clarity and to simplify the representation. The UE 101 may change the eNodeB 103 through which it communicates with the network as it moves about geographically. The MME 109, S-GW 105 and P-GW 107 coordinate to facilitate this mobility of the UE 101 without interruption to any ongoing telecommunication session of the UE 101.
The MME 109 is a control node that, among other duties, is responsible for determining a S-GW 105 that the UE 101 is to communicate with at attach time and when handovers between eNodeBs 103 in the RAN occur. The MME 109 has other responsibilities including idle mode communication with the UE 101, which includes paging and text retransmissions.
The S-GW 105 and the P-GW 107 provide anchor points for a UE 101 enabling various types of transitions that facilitate the mobility of the UE 101 without the UE losing connections with other devices. The S-GW 105 routes and forwards data to and from the UE 101 while functioning as a mobility anchor point for the UE 101 handovers between eNodeBs 103 and between long term evolution (LTE) and other 3GPP technology. The P-GW 107 provides connectivity between the UE 101 and external data packet networks by being a fixed anchor point that offers the UE's Internet Protocol (IP) address into a routable packet network. The S-GW and P-GW may belong to a common operator, or different operators depending on whether the UE is currently being served by a home or visited network.
As shown in the example simplified network of FIG. 1, a UE 101 communicates with the EPC 115 via the eNodeB 103 and reaches a correspondent 113, or 121 via P-GW 107. In this example, the traffic from the UE 101 would traverse the connected eNodeB 103, the S-GW 105, and P-GW 107, to reach a correspondent 113. If the correspondent is a mobile device, the path to that correspondent may also traverse a P-GW, S-GW and eNodeB which are also subtended to the common packet data network. The correspondents 113, 121 can be any device capable of receiving the traffic from the UE 101 and sending traffic to the UE 101 including cellular phones, computing devices and similar devices that may be connected through any number of intermediate networking or computing devices.